932 resultados para Markov chains. Convergence. Evolutionary Strategy. Large Deviations


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This paper deals with exponential stability of discrete-time singular systems with Markov jump parameters. We propose a set of coupled generalized Lyapunov equations (CGLE) that provides sufficient conditions to check this property for this class of systems. A method for solving the obtained CGLE is also presented, based on iterations of standard singular Lyapunov equations. We present also a numerical example to illustrate the effectiveness of the approach we are proposing.

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Local extinctions have cascading effects on ecosystem functions, yet little is known about the potential for the rapid evolutionary change of species in human-modified scenarios. We show that the functional extinction of large-gape seed dispersers in the Brazilian Atlantic forest is associated with the consistent reduction of the seed size of a keystone palm species. Among 22 palm populations, areas deprived of large avian frugivores for several decades present smaller seeds than nondefaunated forests, with negative consequences for palm regeneration. Coalescence and phenotypic selection models indicate that seed size reduction most likely occurred within the past 100 years, associated with human-driven fragmentation. The fast-paced defaunation of large vertebrates is most likely causing unprecedented changes in the evolutionary trajectories and community composition of tropical forests.

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Defaunation, the loss or population decline of medium and large native vertebrates represents a significant threat to the biodiversity of tropical ecosystems. Here we review the anthropogenic drivers of defaunation, provide a brief historical account of the development of this field, and analyze the types of biological consequences of this impact on the structure and functioning of tropical ecosystems. We identify how defaunation, operating at a variety of scales, from the plot to the global level, affects biological systems along a gradient of processes ranging from plant physiology (vegetative and reproductive performance) and animal behavior (movement, foraging and dietary patterns) in the immediate term; to plant population and community dynamics and structure leading to disruptions of ecosystem functioning (and thus degrading environmental services) in the short to medium term; to evolutionary changes (phenotypic changes and population genetic structure) in the long-term. We present such a synthesis as a preamble to a series of papers that provide a compilation of our current understanding of the impact and consequences of tropical defaunation. We close by identifying some of the most urgent needs and perspectives that warrant further study to improve our understanding of this field, as we confront the challenges of living in a defaunated world. © 2013 Elsevier Ltd.

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In this study, we report on a new route of PEGylation of superparamagnetic iron oxide nanoparticles (SPIONs) by polycondensation reaction with carboxylate groups. Structural and magnetic characterizations were performed by X-ray diffractometry (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and vibrating sample magnetometry (VSM). The XRD confirmed the spinel structure with a crystallite average diameter in the range of 3.5-4.1 nm in good agreement with the average diameter obtained by TEM (4.60-4.97 nm). The TGA data indicate the presence of PEG attached onto the SPIONs' surface. The SPIONs were superparamagnetic at room temperature with saturation magnetization (M S) from 36.7 to 54.1 emu/g. The colloidal stability of citrate- and PEG-coated SPIONs was evaluated by means of dynamic light scattering measurements as a function of pH, ionic strength, and nature of dispersion media (phosphate buffer and cell culture media). Our findings demonstrated that the PEG polymer chain length plays a key role in the coagulation behavior of the Mag-PEG suspensions. The excellent colloidal stability under the extreme conditions we evaluated, such as high ionic strength, pH near the isoelectric point, and cell culture media, revealed that suspensions comprising PEG-coated SPION, with PEG of molecular weight 600 and above, present steric stabilization attributed to the polymer chains attached onto the surface of SPIONs. © 2013 Springer Science+Business Media Dordrecht.

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Today, forty years since its birth, the Caribbean integration has reached its limit.1 2 Consequently, there is urgent need to respond to the current realities and emerging global trends — which require greater engagement from the public, students, academics and policymakers — in moving the Caribbean Community towards a new trajectory of Caribbean convergence. The immediate concern is to devise ways of improving the convergence process among Latin American and Caribbean countries. This convergence process will have to be sensitive to both current and emerging global dynamics. This paper presents the roadmap of a new trajectory towards Caribbean convergence, sensitive to both current and emergent regional and global trends. It begins in Section I by identifying the emerging international political and economic trends that provide a backdrop against which the discussion on Caribbean convergence is squarely placed. Section II discusses the need for a new strategy of convergence, and provides the conceptual framework of Caribbean convergence. Section III spells out the pillars, strategies and delivery mechanisms of Caribbean convergence, and highlights the role of Trinidad and Tobago in this process. The paper concludes by pointing out the urgent need for a regional synergy of economic logic and political logic.

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Dynamic Asia has overtaken the European Union as Latin America and the Caribbean’s second largest export market, after the United States. However, the region’s exports to Asia remain concentrated in few commodities involving a small number of large firms. This book explores the present and future scope for the participation of small and medium-sized enterprises (SMEs) in biregional trade and value chains and the measures that can be taken to make those chains more inclusive and sustainable. SMEs have a low direct presence in the region’s export flows and their participation in the supplier networks of multinational companies is weak. This volume reviews several supplier development programmes (SDPs) adopted in various countries in Asia and Latin America to increase SME linkages with multinational firms. These programmes, many of which are public-private initiatives, aim to boost SME productivity and enhance their participation in value chains.

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Aborda, por um lado, a relação entre a economia local no Município de Oriximiná - PA e sua inserção no Comércio Internacional do minério de alumínio. E, por outro, os mecanismos de interação e alianças entre os atores locais público e privado com o setor minerador de alumínio, representado pela Companhia MRN, vis à vis a consecução de um projeto de desenvolvimento local em bases endógenas. O estudo busca compreender como a interação entre interesses públicos/privados, coletivos/individuais, orgânicos/corporativos em âmbito local influenciam no desenvolvimento endógeno do Município. Não obstante, avaliar a dimensão das restrições estruturais, condicionadas pela dinâmica das relações comerciais no setor mundial do minério de Alumínio, aos processos internos de articulação para o desenvolvimento local. O Problema proposto está em compreender como as oportunidades e restrição da explotação de uma mina world class impulsiona processos de desenvolvimento local. Partindo-se da Nova Teoria Econômica aliada à Teoria do Comércio Internacional e Geografia Econômica, buscou-se delinear os parâmetros de inserção da economia mineradora do alumínio local no cenário internacional e suas inter-relações resultantes, sejam estas sob o aspecto tecnológico ou mercadológico. Numa perspectiva local, procurou-se identificar os processos interativos e seu grau de convergência entre Setor Público (via Plano Diretor Municipal) com vistas à concretização de um projeto de desenvolvimento endógeno mediado pela formação de alianças (Clusters) que atendessem às suas respectivas exigências tecnológica, econômica e institucional. Para tanto, o trabalho recorreu às Teorias do Crescimento e Desenvolvimento econômico e dos Sistemas para explicitar os mecanismos que regem as interações entre os atores locais e, em última análise, determinam suas ações sociais no processo de desenvolvimento endógeno. O método adotado é o hipotético-dedutivo utilizando-se instrumentos de coleta de dados secundários e primários. Através de um processo de modelagem computacional e, recorrendo aos Relatórios Fiscais da Prefeitura de Oriximiná e Contábeis da Mineração Rio do Norte buscou-se o aprofundamento sobre a natureza e aplicação dos recursos gerenciados por ambas Instituições. Desenvolve-se ainda, um modelo representativo da dinâmica do desenvolvimento endógeno local tendo o PIB Municipal per capita como proxy através do método de análise multivariada utilizando a técnica da regressão linear múltipla. Desenvolve-se também uma análise da autocorrelação da economia de Oriximiná com o seu entorno a partir da técnica de processamento de dados espaciais geograficamente referenciados bem como a técnica de acessibilidade locacional de Oriximiná. A apresentação dos resultados utiliza modelos simbólicos, tabelas e gráficos diversos. A conclusão é de que a atividade minerária encontra-se descolada do processo de crescimento local por não produzir spillover e por não internalizar o grosso da sua renda no Município dada sua estratégia competitiva. Contudo, a dinâmica local também sofre restrições por conta de sua localização espacial à margem do eixo econômico Regional e pela baixa capacidade empreenditiva e articulatória demonstrada pela administração pública local.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Pós-graduação em Engenharia de Produção - FEB

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Within the framework of the potential of geopark development and the interest of the geological community in creating new areas for geoconservation in Brazil, the aim of this contribution is to show the importance of geoscience education as a strategy for both geoconservation and development, and for the success and maintenance of new geoparks. A historical and evolutionary approach to the theme reveals the current status of geoscience education in Brazil and offers a panorama of the challenges inherent in preparing for the creation of new geoconservation areas. Proposals that aim to promote geoconservation and sustainability in Brazil include projects that capitalize on geological heritage and its relationship with local communities, proposals that form partnerships between the government, universities, businesses, and non-governmental organizations for the development of education, and changes in the law specifically aimed at geoconservation. Improvement in the educational system, including Earth science education, is undoubtedly one of the best strategies to promote the preservation of our natural heritage, and a cultural change in education will certainly promote changes in other areas.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)